Accumulated Other Comprehensive Income - AOCI and Related Tax Effect (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Before Tax Amount
Net change	$ (243)	$ (35)	$ (138)
Tax Effect
Net change	97	14	54
Net of Tax
Net change	(146)	(21)	(84)
Net Unrealized Gains (Losses) on Cash Flow Hedges
Before Tax Amount
Other comprehensive income before reclassifications	(26)	185	130
Reclassifications	(167)	(164)	(91)
Net change	(193)	21	39
Tax Effect
Other comprehensive income before reclassifications	10	(74)	(52)
Reclassifications	68	65	36
Net change	78	(9)	(16)
Net of Tax
Other comprehensive income before reclassifications	(16)	111	78
Amounts reclassified from AOCI	(99)	(99)	(55)
Net change	(115)	12	23
Net Unrealized Gains (Losses) on Securities
Before Tax Amount
Net change	(90)	(11)	301
Tax Effect
Net change	34	5	(118)
Net of Tax
Other comprehensive income before reclassifications	(14)	6	194
Amounts reclassified from AOCI		(12)	(11)
Net change	(56)	(6)	183
Unrealized holding gains (losses) arising during the period on securities available for sale
Before Tax Amount
Other comprehensive income before reclassifications	(40)	(7)	348
Reclassifications	(69)	(20)	(18)
Tax Effect
Other comprehensive income before reclassifications	15	3	(136)
Reclassifications	27	8	7
Net of Tax
Other comprehensive income before reclassifications	(25)	(4)	212
Amounts reclassified from AOCI	(42)	(12)	(11)
Accretion of fair value adjustment on securities available for sale
Before Tax Amount
Other comprehensive income before reclassifications	(1)	(4)	(48)
Tax Effect
Other comprehensive income before reclassifications	0	2	19
Net of Tax
Other comprehensive income before reclassifications	(1)	(2)	(29)
Amortization of net unrealized (gains) losses on held to maturity securities
Before Tax Amount
Reclassifications	20	20	19
Tax Effect
Reclassifications	(8)	(8)	(8)
Net of Tax
Amounts reclassified from AOCI	12	12	11
Foreign Currency Translation Adjustment
Before Tax Amount
Net change	3	(24)	(8)
Tax Effect
Net change	(1)	10	3
Net of Tax
Other comprehensive income before reclassifications		(14)	(5)
Amounts reclassified from AOCI	0	0	0
Net change	2	(14)	(5)
Pension and Other Benefits Adjustment
Before Tax Amount
Net change	37	(21)	(470)
Tax Effect
Net change	(14)	8	185
Net of Tax
Other comprehensive income before reclassifications	(12)	(75)	0
Amounts reclassified from AOCI	35	62	(285)
Net change	23	(13)	(285)
Amortization of prior service credit
Before Tax Amount
Other comprehensive income before reclassifications	(30)	(18)	(15)
Tax Effect
Other comprehensive income before reclassifications	12	6	6
Net of Tax
Other comprehensive income before reclassifications	(18)	(12)	(9)
Recognized net actuarial gain (loss)
Before Tax Amount
Other comprehensive income before reclassifications	89	121	62
Tax Effect
Other comprehensive income before reclassifications	(35)	(47)	(24)
Net of Tax
Other comprehensive income before reclassifications	54	74	38
Pension and other benefits arising during the year
Before Tax Amount
Other comprehensive income before reclassifications	(20)	(124)	(517)
Tax Effect
Other comprehensive income before reclassifications	8	49	203
Net of Tax
Other comprehensive income before reclassifications	(12)	(75)	(314)
Recognized curtailment gain
Before Tax Amount
Other comprehensive income before reclassifications	(2)
Tax Effect
Other comprehensive income before reclassifications	1
Net of Tax
Other comprehensive income before reclassifications	(1)
Accumulated Other Comprehensive Income (Loss)
Net of Tax
Other comprehensive income before reclassifications	(40)	28	267
Amounts reclassified from AOCI	(106)	(49)	(351)
Net change	$ (146)	$ (21)	$ (84)